This invention relates to aerosol containers; and more particularly, to an aerosol container having a pressure relief mechanism on the bottom of the container.
As is known in the art, aerosol containers are made of a metal, typically steel, and are used to store a product, under pressure, and then dispense the product, typically in the form of a foam or a spray. Such containers are either of a two-piece or a three-piece construction and include a body comprising a hollow cylinder and end pieces. In a two piece container, the cylinder is closed at one end and an end piece is attached to the other, open end of the container with a circumferential seam, usually a double seam, formed about the periphery of the two pieces to join them together. In a three-piece container, the cylinder is open at both ends and with end pieces attached to the respective ends of the cylinder, again by seaming. The cylinder of the container is filled with both a product to be dispensed from the container, and a propellant for expelling the product. A valve assembly is carried by an end piece and, when activated, the product is dispensed through a valve of the assembly.
The product and propellant are held under pressure in the container. The double seam forms a mechanical joint between the two parts of the container. If the container is subjected to a pressure which exceeds its design limits, the seam will come apart (release) before the container body splits open. The container will then be said to have “burst” and the potential energy stored within the container is converted into kinetic energy and released. When this happens, there can be a sudden and energetic release of the bottom end piece of a container from the container.
One way to prevent a can from bursting is to vent the pressure before the container bursts. In this regard, it is known that one way to provide the pressure relief to vent a container is to inscribe a score mark or line somewhere on the container so to form an area of reduced thickness, or weakness in the container wall, which will give when the internal container pressure exceeds some pressure limit. In U.S. Pat. No. 3,850,339, for example, a pressure relief system for containers includes a plurality of scoring marks formed in the seam where the container body and valve end of the container are joined together. When the internal pressure in a filled container exceeds the pressure limit, the periphery of this top closure buckles outwardly causing fracturing that produces a plurality of vents. This allows the contents of the container to safely escape and prevent the end of the container from blowing-off.
More recently, U.S. Pat. No. 7,222,757 describes a container in the base of which an arcuately shaped score line is made. This score line produces an area of reduced thickness in the bottom wall of the container which fractures when the container is subjected to an over-pressure, again allowing the container to vent its contents to the atmosphere rather than bursting.
While effective for its intended purpose, the constructions shown in these patents are not applicable to all aerosol container constructions.